Note On High Precision Stellar Aperture Photometry

Although photometry is not a part of astrometry, the photometric result of natural satellite during the period of their mutual occultation and eclipse can contribute to the accurate astrometry. Given to the configuration of natural satellites, we select aperture photometry from major methods as our main study contents. Base on the work of previous researchers, the procedure and experimental experience of photometry are described in detail, including star centering, background estimation, instrumental magnitude calculation, aperture correction and so on.Using the photometric procedure designed by ourselves, we measure 72 CCD images which were taken by the 1-m telescope at Yunan observatory. The results show that the average internal precision is about 0.003mag for bright stars (-10mag) and 0.2mag for faint stars (-17mag). The comparison with the photometry software package APPHOT in IRAF is made as well. We find that the average internal precision from our growth curve is equal to that derived from APPHOT for bright stars. For middle-brightness stars or faint stars, growth curve delivers a little better magnitude than APPHOT. And the systemic deviation between two measuring systems is rather small after using growth curve.Summing up the experimental experience, we find that a photometric procedure needs precise star centering. Background estimation is also important. Besides, both histogram and the "3-2" formula are good methods. The linear weight of the pixel intensity can contribute to the improvement of precision. Finally, using a growth curve from bright stars to correct the instrumental magnitude can improve measure precision of faint stars quite well.